I think this may not be a big deal.
You don't have to have a forced unified system to have a unified log-in and shared awards/boards.
Its very possible Nintendo is making the interface that will then accept the online solution/server connections any 3rd party wants to implement.
All the 3rd parties will need to do is accept the login credentials and any game related metadata for leader-boards and some award system. (probably coin or star related)
I think its way too early with far too little info to make a judgement at this time.